Basement membranes are
specialized extracellular matrices that are essential for epithelial structure
and morphogenesis. However, little is known about how the newly synthesized
proteins are targeted to the basal cell surface or how this process is
regulated during development. Working in
the Drosophila follicle cell
epithelium, we have found that basement membrane proteins are synthesized in a
basal endoplasmic reticulum compartment from localized mRNAs. The proteins are then trafficked through the
basal cytoplasm using a Rab10-dependent mechanism. Interestingly, the specific basement membrane
that we study also undergoes structural changes during development to create
fibril-like structures that drive tissue elongation. Our
preliminary data suggest that a switch in the location where basement membrane
proteins exit the cell, from the basal to lateral surface, may control fibril
formation. Thus, studies of this
matrix remodeling event may reveal how choreographed changes in a cellular secretion
program can help shape tissues and organs during development.